Which of these groups lists three good electrical insulators?

An electrical insulator is a material that strongly resists the flow of electric current. These materials have tightly bound electrons that do not move freely, making them ideal for protecting circuits and preventing unintended electrical shorts. Glass, air, and porcelain are classic examples of excellent insulators. Porcelain and glass are widely used to suspend high-voltage power lines and antenna wires, while air naturally insulates the gaps between conductive elements. The other options are incorrect because they each contain at least one conductive material. Copper, carbon, and aluminum all permit electric current to flow easily, making them completely unsuitable as insulators.